Reticulospinal Tract and Resistance Training: A Summary

Reticulospinal Tract and Resistance Training

Introduction

  • Resistance training increases force production, partly due to central nervous system adaptations.
  • The reticulospinal tract (RST) may mediate adaptation to resistance training.
  • This review discusses the RST's potential role in muscle strength adaptations.

Anatomy and Function of the Reticulospinal Tract

  • The RST is a major descending tract involved in gross motor function and forceful movements.
  • It allows for bilateral innervation of axial and appendicular muscles.
  • RST facilitates the execution of forceful movements, contrasting with the corticospinal tract (CST) for fine motor control.
  • RST polysynaptic MEP amplitudes were also found to be five times lower than the monosynaptic CST connections.
  • The asymmetric tonic neck reflex activates cervical afferents and facilitates the RST.

Evidence of Reticulospinal Tract Plasticity in Nonhuman Primates

  • Lesioning studies in monkeys showed that RST lesions impair gross motor function.
  • Stimulation of the reticular formation increased postsynaptic amplitudes, aiding motor function recovery after CST lesioning.
  • Resistance training in monkeys increased RST responses, suggesting stronger connections.

Measuring Reticulospinal Tract Function in Humans

  • The StartReact paradigm quantifies the ergogenic effect of a startling auditory stimulus (SAS) on reaction time.
  • When a SAS precedes TES of the motor cortex by 80 ms, the MEP response in FDI is facilitated.
  • Ipsilateral cortical magnetic stimulation can indirectly activate the RST via the cortico-reticulospinal pathway.

Evidence That the Reticulospinal Tract Might Undergo Adaption to Resistance Training in Humans

  • Stroke patients show increased RST efficacy to compensate for CST lesions.
  • SCI patients show reduced reaction times during high force tasks, indicating RST involvement.

Limitations of Resistance Training Literature in Humans

  • Studies on CST adaptation to resistance training show variable results.
  • Focus on distal muscles may bias observations in favor of CST adaptation.
  • Use of untrained participants and external auditory pacing may confound results.

Summary and Future Directions

  • The RST is an understudied site of neural adaptation to resistance training.
  • Indirect testing methodologies show promise in elucidating RST function.
  • Animal studies and human functional recovery studies suggest the RST mediates gross motor function and high force generation.
  • Future research should focus on both CST and RST function to better understand neural adaptation to resistance training.